Crohn's disease is a chronic, inflammatory condition of the gastrointestinal tract with an estimated incidence of 5 per 100,000/year. The current standard of practice in treating newly diagnosed Crohn's disease follows a stepwise escalation of therapies from less potent drugs with fewer side effects to more effective medications considered to carry greater risk. A rationale may exist for treating the disease with the most potent medications soon after diagnosis in order to arrest the development of complications which frequently necessitate surgery early in the disease. The proposed protocols will investigate the rationale for a new therapeutic strategy in the treatment of new-onset Crohn's disease. Specifically, the described studies will provide necessary pilot feasibility data to design a community-based, randomized controlled comparison of standard, step-wise therapy to early intervention with the immunomodulatory drug, 6-mercaptopurine. The feasibility of this trial will be determined by: 1) defining the current standard of practice of initial medical therapy for Crohn's disease; 2) determining the annual incidence of Crohn's disease within cooperating gastroenterology practices in New England; 3) ascertaining the incidence of surgical endpoints to provide a basis for sample size estimates; 4) identifying risk factors which, early in the course of the disease, may be associated with increased risk of surgery; and 5) demonstrating the feasibility of achieving adequate patient accrual through mock informed consent procedures. In completing these studies it is hoped that sufficient preliminary data will be obtained to design and organize a randomized, controlled trial of early use of immunomodulatory therapy in the treatment of Crohn's disease.